How long will it be before it is a case of Northern sole in the Aviva Premiership? Never mind the fizz of the Heineken Cup this weekend, Newcastle and Leeds face each other at Kingston Park on Saturday with the loser going into the final few rounds of the season at the bottom of the table and relegation beckoning. Hardly small beer.

With Sale perched uncomfortably above the bottom two and Worcester or Cornish Pirates likely to win the Championship, it is little wonder that the former Newcastle wing John Bentley, who is Leeds's community marketing manager, says he fears for the future of rugby union in the north of England and the three Premiership clubs based there are struggling for media coverage at a time when transport costs are a factor.

"The team I was part of at Newcastle was like a who's who of the game and we were able to buy a squad to compete at the top level," Bentley says. "With the exception of Worcester, I am not sure about the appetite from other clubs to build the infrastructure or spend the money to do that now. The game has moved on and we are in danger of undoing a lot of the good work that has gone on to build the brand of the Premiership and the raising of the standards within the game in key areas.

"I realise I am speaking with a vested interest but until you are involved at a club that could go out of the Premiership you don't appreciate how much damage it can do. It is desperately sad to see two clubs who not only represent their city but their region in the Aviva Premiership battling it out for survival. I do fear for the game in the north if we are not represented in the top level because I think the game needs a geographical spread across the whole country."

Leeds looked doomed when they lost at home to Newcastle at the end of February, but they have won two of their four games since then, picking up nine points, while the Falcons have taken four points from three matches. It is hard to see Leeds recovering if they lose on Saturday with a trip to Northampton among their final three matches and they will need to win away in the Premiership for the first time in a year.

They have harvested a mere four points on the road in the league this season having started by being within a couple of minutes of defeating Gloucester at Kingsholm and they came within a try of winning at Bath and Sale. Their away form last season, when they won at London Irish, Sale, Newcastle and Wasps was a major factor in their staying up – it is now a reason why they are in very real danger of a return to the Championship.

Leeds, like Newcastle, struggle to attract capacity crowds and on the day they provide a spectacle for ghouls, the two teams who have spent virtually all the season at the top of the Premiership, Northampton and Leicester, carry the English flag in the Heineken Cup. The Tigers are in Dublin on Saturday and the Saints entertain Ulster in Milton Keynes the following afternoon.

Leicester and Northampton are among the four Premiership clubs who want the salary cap either abolished or raised significantly. Leeds and Newcastle are two of the sides resolutely opposed to any change and this weekend shows how marked the ambitions of the quartet are.

Leicester and Northampton want to dine at Europe's top table; Newcastle and Leeds's menu is simpler: survival. The Saints appreciate how life can be at the bottom. Relegated in 2007, their plight then was down to poor management and recruitment rather than a shortage of money. They spent unwisely.

They gorged themselves on foreign fare then but their diet is now more English, even if that brings different problems with players on international duty for a big chunk of the season. Newcastle not that long ago had a core of home grown players, Jonny Wilkinson, Toby Flood, Mathew Tait, Jamie Noon and Tom May, supplemented by major overseas recruits such as Matthew Burke and Carl Hayman, but their budget now does not stretch much beyond Poundland.

Flood is at Leicester, joined next season by Tait and May is on his way to Northampton. The point of the salary cap was not just to ensure that some clubs did not slide into unmanageable debt in order to try to keep up but to provide a balance in the Premiership that minimised the difference between the haves and the have-nots.

Excluding Bath, who won the title in 1996 at the end of what was a vacuum year, only four clubs have won the title in the professional era: Leicester, Wasps, Newcastle and Sale. Success proved a one-off for the Falcons and the Sharks but if the Premiership was aspirational then, empowered as a collective, the stresses now are threatening to make it each club for itself.

Owners stress they are running a business, but if normal business practice applied and rivals were eliminated, where would that leave those who survived? En route to a European super league? Unlikely given the value the French place on the Top 14. The emphasis should be on keeping the Premiership strong, but as the better off clubs grow frustrated by the purchasing power of the leading clubs in France, they become less bound by collective will.

The Premiership has looked at various ways of amending the salary cap. One proposal would have allowed clubs to be bound by the restriction on wages only in the Premiership, allowing them greater resources for Europe but that would amount to a maximum of nine matches a season.

It got nowhere, but there is no obvious compromise when it comes to the cap. A strength of the Premiership has been that the clubs are in it together, helping them take on the Rugby Football Union in the past, but if this weekend's two English Heineken Cup quarter-finalists come to see the likes of Newcastle and Leeds as dragging them down, the dynamic will change.

World of opportunity

Rugby at Test level has not changed much over the years. New Zealand and South Africa are at the top of the world rankings and they have comfortably the two best records in the history of the international game. Australia are third with the Six Nations sides jostling underneath.

What is different from 50 years ago is that the World Cup has provided Argentina and the Pacific islands with a platform and the home championship has been swelled by the introduction of Italy. Otherwise Test rugby looks pretty much the same.

And yet. The World Cup is making a difference. The first tournament, held in New Zealand in 1987, yielded a surplus of £1m. That had swollen 20 years later to one of more than £122m. It will be higher again after this year's tournament in New Zealand, even though the host union will struggle to make a profit.

The World Cup surplus is used by the International Rugby Board to invest in the world game. A report for the governing body by the Centre for the International Business of Sport at Coventry University published this week showed that participation in the sport had increased by 19% since the last World Cup.

Rugby union's inclusion in the Olympics should add to the swell, with countries now having access to funding that was previously denied them. If you compile a world top 10 in terms of playing population, it looks different to the normal rankings, including Sri Lanka and the United States as well as Japan and missing Wales, Scotland and Italy.

When the late Vernon Pugh was the chairman of the IRB, his prime ambition was to get rugby into the Olympics. He saw the US and China as potential powerhouses if their unions had access to the public funds that would result from membership, opening up significant television audiences.

That dream is now a step closer to reality. The game in China is growing but it remains small, with fewer than 5,000 participants. Sevens will be used to grow the game from 2013, included in the Chinese National Games programme as well as the development system, while the 2019 World Cup in Japan will act as a stimulus in Asia.

The US has seen a 350% increase in participation since 2004. The World Cup will be shown live on national television nationwide for the first time this year with a deal also in place for 2015 and Sevens has had a major impact economically on host cities.

The USA play Russia in this year's World Cup. The match will have no bearing on the outcome of the tournament but it will help enrich the group stage. Moscow will host the Rugby World Cup Sevens in 2013 and the government has agreed to build new stadiums for the tournament. The game is also growing in Georgia.

New Zealand need not fret yet but rugby's landscape should look very different in 50 years from how it did half a century ago. Its world has been far too small.